Abstract
Due to their high theoretical energy density, direct borohydride fuel cells (DBFCs) are a promising alternative to proton exchange membrane fuel cells for mobile applications. However, the energy conversion efficiency of DBFCs is impeded by the hydrogen generation and escape from the anode upon operation. The hydrogen escape characteristics during the BOR depend strongly on the type of metal chosen as anode electrocatalyst, on the architecture of the catalyst layer and on the concentration of NaBH4 [1-4]. This shows the importance for further understanding of the BOR mechanism with regards to the influence of the experimental conditions on the reaction.In this presentation, the results of recent experimental studies about the BOR on gold and platinum electrodes will be presented and discussed with the help of microkinetic modeling. The proposed kinetic model is able to reproduce the main features of electrochemical (rotating (ring-)disk electrode, RRDE) and differential electrochemical mass-spectrometry (DEMS) measurements for various concentrations of NaBH4 (5, 50 and 500 mM), and is in agreement with the results of DFT calculations and FTIR measurements [5-8]. These experimental findings enable to compare and discuss the BOR mechanism between Pt and Au surfaces accounting for the differences in hydrogen generation/oxidation during the BOR but also for the poisoning of the electrodes with adsorbed BOR intermediates. This work was supported by the French ANR (project ANR-16-CE05-0009). References (1) Jusys, Z.; Behm, R. J. Electrochem. Commun. 2015, 60, 9.(2) Freitas, K. S.; Concha, B. M.; Ticianelli, E. A.; Chatenet, M. Catal. Today 2011, 170, 110.(3) Olu, P.-Y.; Job, N.; Chatenet, M. J. Power Sources 2016, 327, 235.(4) Olu, P. Y.; Bonnefont, A.; Rouhet, M.; Bozdech, S.; Job, N.; Chatenet, M.; Savinova, E.Electrochim. Acta 2015, 179, 637.(5) G. Rostamikia, M.J. Janik, J. Electrochem. Soc., 2009, 156 B86.(6) G. Rostamikia, M.J. Janik, Electrochim. Acta, 2010, 55, 1175.(7) B. Molina Concha, M. Chatenet, F. Maillard, E.A. Ticianelli, F.H.B. Lima, R.B. de Lima,Phys. Chem. Chem. Phys., 2010, 12, 11507.(8) B. Molina Concha, M. Chatenet, E.A. Ticianelli, F.H.B. Lima, J. Phys. Chem. C, 2011, 115 12439.
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